The present invention relates to pigment mixtures comprising at least two components, component A being SiO2 flakes coated with one or more metal oxides and/or metals and component B being platelet-shaped, acicular or spherical colorants and/or fillers, and to their use in varnishes, paints, printing inks, plastics, powder coating materials and cosmetic formulations.
With platelet-shaped pigments, hiding power and gloss are often difficult to realize simultaneously to a satisfactory extent. For instance, SiO2 flakes or mica platelets covered with one or more thin metal oxide layers feature interference colors and a high luster but at the same time, owing to the transparent substrate, feature high transparency and hence a comparatively poor hiding power.
DE-A-42 40 511 discloses a pigment mixture which is composed of an interference pigment and a platelet-shaped color pigment. The interference pigment comprises mica flakes or SiO2 flakes coated with metal oxides and the color pigment can be colored SiO2 flakes. This pigment mixture is incorporated into coating materials, printing inks or plastics.
It is an object of the present invention to provide a pigment mixture which is notable for a comparatively high hiding power, which lends itself well to incorporation into the respective system in which it is used and for which at the same time the separation of pigment/colorant in the system is minimal.
Surprisingly, a pigment mixture has now been found which has none of the disadvantages indicated above. The pigment mixture of the invention comprises at least two components, component A being SiO2 flakes coated with one or more metal oxides and/or metals and component B being platelet-shaped, acicular or spherical colorants or fillers. By admixing the colorant to the coated SiO2 flakes it is possible to give the systems in which they are used a multiple flop, the color effect is intensified, and new color effects are achieved. As used herein, the term xe2x80x9cmultiple flopxe2x80x9d refer to color changes as a function of viewing angle.
The invention thus provides a pigment mixture comprising at least two components, component A being SiO2 flakes coated with one or more metal oxides and/or metals and component B being platelet-shaped, acicular or spherical colorants or fillers. By spherical is meant a range of substantially spherical shapes including, e.g., perfect spheres, indented or deformed spheres, etc.
The invention likewise provides formulations, such as paints, varnishes, printing inks, plastics, powder coating materials and cosmetic formulations, which comprise the pigment mixture of the invention.
The coated SiO2 flakes can be mixed with the colorant and/or filler in any ratio. Preferably, the (wt/wt) ratio of component A to component B is about 1:10 to 10:1, in particular about 1:2 to 2:1.
The SiO2 flakes produced on a continuous belt in accordance with WO 93/08237 are based on a platelet-shaped, transparent, colored or colorless matrix and typically possess a thickness of about 0.1 to 5 xcexcm, in particular about 0.2 to 2.0 xcexcm. The length in the two other dimensions is typically about 1 to 250 xcexcm, preferably about 2 to 100 xcexcm and, in particular, about 5 to 40 xcexcm. The SiO2 flakes are provided with one or more metal oxide layers an/or metal layers. Examples of suitable metal oxides or metal oxide mixtures are, e.g., titanium oxide, zirconium oxide, zinc oxide, iron oxides and/or chromium oxide, especially TiO2 and/or Fe2O3. The SiO2 flakes can be coated as described, for example, in WO 93/08237 (wet chemical coating) or DE-A-196 14 637 (CVD process).
The outer metal oxide layer can also be a semitransparent metal layer. Metals suitable for this purpose are, for example, Cr, Ti, Mo, W, Al, Cu, Ag, Au and Ni. Metals can be coated on the SiO2 flakes by conventional methods, e.g., physical vapor deposition (PVD). Preferred pigments have the following layer structure: SiO2 flakes+metal+SiO2+metal oxide.
In order to bring out special color effects, fine particles in the nanometer size range can be introduced into the metal oxide layers of high or low refractive index. Examples of pigments suitable for this purpose are, e.g., finely divided TiO2 or finely divided carbon (carbon black) with particle sizes in the range of about 10 to 250 nm. Through the light-scattering properties of such particles it is possible to exert a controlled influence on luster and hiding power.
Colorants suitable as component B for the pigment mixture of the invention are all acicular and spherical colorants which are known to the skilled worker and have a particle size of about 0.001 to 10 xcexcm, preferably about 0.01 to 1 xcexcm. The pigment mixtures of the invention preferably comprise, as colorants, absorption materials and/or fillers.
The spherical colorants can be, e.g., TiO2, colored SiO2, CaSO4, iron oxides, chromium oxides, carbon black or organic color pigments, such as anthraquinone, quinacridone, diketopyrrolopyrrole, phthalocyanine, azo and isoindoline pigments. The acicular pigments can be, e.g., BiOC1, colored glass fibers, -Fe3O4, or organic color pigments, such as azo pigments, xcex2-phthalocyanine CI Blue 15.3, Cromophtal Yellow 8GN (Ciba-Geigy), Irgalith Blue PD56 (Ciba-Geigy), azomethine copper complex CI Yellow 129, and Irgazine Yellow 5GT (Ciba-Geigy).
Cosmetic formulations (especially decorative formulations) preferably comprise, not only colorants and SiO2 flakes, but also fillers (one or more) or mixtures thereof in amounts (wt/wt) of about 1-50%, preferably about 1-30% and most preferably, about 1-15%, based on the overall solids content of the system.
Suitable fillers can be, e.g., mica, talc, TiO2 and mica, TiO2+BaSO4+mica, mica+silica, silica, silica+TiO2+Fe2SO3, BiOC1, BiOC1+mica, or BiOC1+talc. Some of these products are obtainable, e.g., under the trade names of Merck KGaA: Ronasphere(copyright), Ronasphere(copyright) LDP, Micronasphere(copyright) M, Silk Mica, Satin Mica, Naturaleaf Powder, Low Luster Pigment, Extender W, Talkum feinst gepulvert [finely powdered talc], Biron(copyright), Bital(copyright) and Mibiron(copyright). Other fillers can be, e.g., nylon-12 (from Elf Atochem), nylon-6 (from Elf Atochem), boron nitride, Nylon Powder (from Elf Atochem), polyamide 12 (from Kobo), polyethylene (from Kobo), PTFE (from Presperse), lauroyl lysine (from Ikeda), polymethyl methacrylate (from Ikeda) or calcium aluminum borosilicate (from Presperse).
The pigment mixture of the invention is simple and easy to handle. The pigment mixture can be incorporated into the system in which it is used simply by stirring it in. Laborious milling and dispersing of the pigments is not necessary.
The pigment mixture of the invention can be used, e.g., for pigmenting coating materials, printing inks, plastics, agricultural films, the coating of seeds, food colorings, button pastes, medicament coatings or cosmetic formulations. The concentration of the pigment mixture in the system in which it is to be used for pigmenting is typically about 0.1 to 70% by weight, preferably about 0.1 to 50% by weight and, in particular, about 1.0 to 10% by weight, based on the overall solids content of the system. It is generally dependent on the specific application.
Plastics comprising the pigment mixture of the invention in amounts of about 0.01 to 50% by weight, in particular about 0.1 to 7% by weight, based on the overall solids content of the system, are notable for a particular sparkle effect.
In the coating sector, especially in automotive finishing, the pigment mixture can be employedxe2x80x94for 3-coat systems as wellxe2x80x94in amounts of about 0.1 to 10% by weight, preferably about 1 to 3% by weight, based on the overall solids content of the system. The proportion in which the coated SiO2 flakes are mixed with component B depends on the desired effect. The SiO2 flakes are preferably employed with component B in a proportion (wt/wt) of about 1:4, in particular of about 1:3.
In a coating material, the pigment mixture of the invention has the advantage that the desired color flop effect is achieved by a single-layer coating (one-coat system or base coat in a two-coat system). This color flop is extremely pronounced even under diffuse light. In comparison with coating systems which comprise a mica-based interference pigment rather than the coated SiO2 flakes, coating systems with the pigment mixture of the invention exhibit a more marked depth effect and a glitter effect.
The pigment mixture of the invention can also be employed in decorative and grooming cosmetology. For this embodiment, component B colorants can be, e.g., organic or inorganic color pigments or dyes, of natural or synthetic origin, such as, e.g., chromium oxide, ultramarine, or spherical SiO2 or TiO2 pigments. The concentration of the components and the proportion of SiO2 flakes to component B are dependent on the medium in which they are used and on the effect that is to be achieved. The SiO2 flakes can be mixed with component B pigments in any proportions, the preferred ratio being about 1:10 to 10:1 (wt/wt). The use concentration of SiO2 flakes can range from about 0.01% by weight in a shampoo to about 70% by weight in a compact powder, based on the overall solids content of the system. In the case of a mixture of SiO2 flakes with spherical fillers, such as SiO2, the concentration in the formulation can be about 0.01 to 70% by weight. The cosmetic products, such as nail varnishes, lipsticks, compact powders, shampoos, loose powders and gels, are notable for particularly interesting luster effects and/or color effects. The glitter effect in nail varnish can be increased markedly relative to conventional nail varnishes with the aid of the pigment mixtures of the invention. Furthermore, the pigment mixture of the invention can be employed in bath products, in toothpastes and for enhancing foods, for example as a mass colorant or as a coating.
In the pigmentation of binder systems for, for example, paints and printing inks for intaglio, offset or screen printing, or as a precursor for printing inks, in the form for example of highly pigmented pastes, granules, pellets, etc., pigment mixtures, especially those comprising coated SiO2 flakes with spherical colorants, such as TiO2, carbon black, chromium oxide, iron oxide or organic color pigments, have been found particularly suitable. The pigment mixture is typically incorporated into the printing ink in amounts of about 2 to 35% by weight, preferably about 5 to 25% by weight and, in particular, about 8 to 20% by weight, based on the overall solids content of the system. Offset printing inks may comprise the pigment mixture in an amount of up to about 40% by weight or more. The precursors of printing inks, in the form for example of granules, pellets, briquettes, etc., can contain up to about 95% by weight of the pigment mixture of the invention, not including the binder and additives. The mixing ratio of component A to component B is preferably about 1:10 to 10:1. The printing inks comprising the pigment mixture of the invention exhibit purer hues and their printability is improved owing to the good viscosity values.
The invention hence also provides formulations comprising the pigment mixture of the invention.
In the foregoing and in the following examples, all temperatures are set forth uncorrected in degrees Celsius; and, unless otherwise indicated, all parts and percentages are by weight.
The entire disclosure of all applications, patents and publications, cited above and below, and of German application No. 198 23 864.9 filed May 28, 1998 is hereby incorporated by reference.